Wing panels constituting wing surfaces are mounted above and below beam members, thereby assembling a main wing of the aircraft into a hollow structure. Generally an internal space of the main wing is used as a fuel tank.
An opening is formed in the surface of the main wing in order to perform inspection, maintenance and the like of an inside of the fuel tank. The opening is normally closed by an access door, and the access door is opened in performing the inspection, maintenance and the like (for example, see Non-Patent Document 1).
The access door includes a door body that is disposed on an internal space side of the main wing with respect to the opening and a clamp ring that is disposed on an external side of the main wing with respect to the opening.
Each of the door body and the clamp ring has an external dimension larger than that of the opening. The door body and the clamp ring are tightened by a fastener member and the like while an edge portion of the opening is held between an outer circumferential portion of the door body and an outer circumferential portion of the clamp ring, whereby the opening is closed by the door body.